OO PHP plus OO MySqli

[php-beginner]

Hello everyone,

 

For two weeks now, I'm trying to get this database connection in my query. Can someone give me a solution and tell me what I've done wrong? Am I overlooking something?

 

<?php

class Mysql{
public function connect(){
	$mysqli = new mysqli('localhost','root','','login');
}
}

class Query extends Mysql{
public function runQuery(){
	$this->result = parent::connect()->query("select bla bla from bla bla");
}
}

$query = new Query;
$query->runQuery();

?>

[ignace]

You are not returning or saving the connection:

 

class DbMySQLi {
    private $connection;
    
    public function connect() {
        if(is_null($this->connection)) {
            $this->connection = new mysqli('localhost', 'root', '', 'login');
        }
        return $this->connection;
    }
}

class Query extends DbMySQLi {
    private $result;
    public function runQuery() {
        $this->result = $this->connect()->query('SELECT * FROM bla');
    }
}

$query = new Query();
$query->runQuery();

[php-beginner]

Thanks!

 

So I always have to return the value that i have created for another variable?

[ignace]

Thanks!

 

So I always have to return the value that i have created for another variable?

 

No, a class is a container of variables and functions. I could establish the DB connection in the constructor and all methods would have access to the DB connection.

[php-beginner]

Thanks!

 

So I always have to return the value that i have created for another variable?

 

No, a class is a container of variables and functions. I could establish the DB connection in the constructor and all methods would have access to the DB connection.

 

Then why is it necessary in this case? (sorry for the lame questions)

[ignace]

Then why is it necessary in this case? (sorry for the lame questions)

 

It isn't, I just extended upon your example.

[php-beginner]

Then why is it necessary in this case? (sorry for the lame questions)

 

It isn't, I just extended upon your example.

 

Ah ok.

 

But i don't want to store all methods in one class because then it is not object oriented right? So, why is this necessary in my example?

[ignace]

Your class can have multiple methods and class variables you just have to make sure the methods are cohesive (related) towards the class and one another.

[php-beginner]

Ok,

 

Thankyou for your patience and solving my problem.

 

I still have one question open . Why do i have to return the value in the example given?

 

    public function connect() {
        if(is_null($this->connection)) {
            $this->connection = new mysqli('localhost', 'root', '', 'login');
        }
        return $this->connection;

[ignace]

Because in your code you call:

 

$this->connect()->query('SELECT * FROM bla');

 

If you don't return the value the above wouldn't work. You could rewrite it making the connection in the constructor or something and making the connection protected and call it like:

 

$this->connection->query('SELECT * FROM bla');

 

Your code would look then like:

 

class DbMySQLi {
    protected $connection;
    
    public function connect() {
        $this->connection = new mysqli('localhost', 'root', '', 'login');
    }
}

class Query extends DbMySQLi {
    private $result;
    public function runQuery() {
        $this->result = $this->connection->query('SELECT * FROM bla');
    }
}

[php-beginner]

By making the connection in the constructor, you mean saving it in the connection variable?

 

This code will give me the following error: Fatal error: Call to a member function query() on a non-object

 

What's wrong?

[ignace]

I forgot to add the constructor, here it is again:

 

class DbMySQLi {
    protected $connection;
    
    public function __construct() {
        $this->connect();
    }
    
    public function connect() {
        $this->connection = new mysqli('localhost', 'root', '', 'login');
    }
}

class Query extends DbMySQLi {
    private $result;
    public function runQuery() {
        $this->result = $this->connection->query('SELECT * FROM bla');
    }
}

[php-beginner]

Thankyou so much!

[php-beginner]

I have marked this problem solved. But i hope you still want to answer my last question.

 

Why do i have to return returnQuery() ? And why don't i have to return runQuery() ?

 

<?php

class Mysql{

protected $db;

public function __construct(){
	$this->db = new mysqli('localhost','root','','login');
}
}

class Query extends Mysql{

private $result;

public function runQuery($query){
	$this->result = $this->db->query($query);
}
public function returnQuery(){
	return $this->result->num_rows;
}
}

class User{

private $query; // Instantiate Query object.

public function __construct(){
	$this->query = new Query;
}
public function login(){
	$this->setQuery = "select userid from users where username = 'wouter' and password = 'test'";
	$this->query->runQuery($this->setQuery);

	if($this->query->returnQuery() > 0){
		echo "You are logged in!";
	}else{
		echo "Wrong username / password!";
	}
}
}

?>